Tissue fixation devices are used extensively to repair traumatic injuries, for example, those sustained during sporting events. Such “sports medicine fixation devices” are typically used to fix soft tissue and sometimes hard tissue back to bone. Sports medicine implants may be used to repair bone, chondral and/or osteochondral defects.
Bioabsorbable materials are used in both types of applications. For example, interference screws are used to fixate autologous grafts during anterior cruciate ligament (ACL) repair. The devices are often made from a semicrystalline polymer, poly(l-lactic acid) (PLLA) or copolymers of PLLA with poly(d,l-lactic)acid (PDLA) or poly(glycolic)acid (PGA). These bioabsorbable polymers produce acidic products upon degradation, and others have suggested inclusion of a buffering compound to neutralize the breakdown products (see, e.g., U.S. Pat. No. 6,741,329). Although appropriate for soft tissue repair, these materials can also be used in the event of orthopedic trauma or reconstructive surgery to fixate bone to bone.
The ideal bioabsorbable has sufficient mechanical properties to perform its primary function but over time the implant should ideally get replaced by natural tissue that is surrounding the implant. It certain embodiments the material releases compounds that aid the repair and replacement process.